1. Field of the Invention
The present invention relates to a master carrier for magnetic transfer, a magnetic transfer apparatus, and a magnetic transfer method, which are employed in magnetic transfer, which is realized by placing a master carrier bearing transfer information, and a slave medium in close contact.
2. Description of the Related Art
Magnetic transfer, which is the subject of the present invention, is a process by which magnetic patterns are transferred and recorded onto slave media. The transfer and recording are realized by placing a master carrier (patterned master) having an uneven transfer pattern, for example, servo signals in the form of protrusions and recesses, which has a magnetic layer at least on its surface in close contact with a slave medium having a magnetic recording portion. A transfer magnetic filed is applied to the master carrier and the slave medium in this state of close contact, and a magnetic pattern corresponding to the information borne by the master carrier is transferred and recorded onto the slave medium.
In the case that the slave medium is a discoid medium, such as a hard disk or a high density flexible disk, the master carrier is also of a discoid shape. The transfer pattern is formed as a concentric pattern on the discoid master carrier. The master carrier is placed into close contact with a single side of the slave medium, or two master carriers are placed into close contact with both sides of a slave medium. A magnetic field applying device, comprising electromagnets or permanent magnets, is provided on either one or both sides of the master carrier and the slave medium in this state of close contact, and a transfer magnetic field is applied (refer to U.S. Pat. No. 6,636,371, for example).
In order to improve the transfer quality of the above magnetic transfer, it is necessary that the interval between the surfaces of the master carrier and the slave medium is uniform. The master carrier and the salve medium are placed in close contact for this reason. During close contact, the entirety of the surfaces must be in uniform close contact, and positional displacement must not occur.
If the master carrier and the slave medium move relatively in a sliding manner when they are placed in close contact, desired signals cannot be transferred and recorded at predetermined positions. In the case that the signals are servo signals, sufficient tracking functions cannot be obtained, thereby decreasing the reliability of the finished product. In addition, the master carrier may become contaminated, or the surfaces of the master carrier and the slave medium may become damaged. This is due to the friction that occurs between the master carrier and the slave medium during their relative sliding motion while a close contacting force is applied thereto.
Meanwhile, after magnetic transfer is completed, the close contact between the master carrier and the slave medium is released, and they are separated from each other. However, if the degree of close contact between the master carrier and the slave medium is excessive, there are cases in which loads are applied on the master carrier and the slave medium, causing damage thereto. That is, it is necessary that the master carrier and the slave medium does not slide to cause positional displacement when they are placed into close contact. Yet, close contact states that do not allow any sliding at all cause problems during separation.
Master carriers, which are the subject of the present invention, comprise uneven patterns formed by protrusions and recesses. The close contact friction properties differ according to the degree of unevenness and other surface properties. However, it is unknown what manner of surface properties would enable favorable close contact states with slave media.